This invention relates to an intake system for an internal combustion engine and more particularly to an improved engine induction system that improves performance throughout the engine speed and load ranges.
It is well known that the design of an engine induction system represents a compromise between good running at low and medium engine speeds and maximum performance. In order to achieve good running at low and medium speeds, a relatively small induction system is desirable so as to provide high gas flow velocities into the combustion chamber to increase turbulence and improve flame propagation. On the other hand, an engine that is designed to achieve high maximum outputs has a relatively large effective cross-sectional area induction system so as to insure maximum air breathing at wide open throttle conditions. In order to try to obtain the advantages of both systems, it has been proposed to provide an engine induction system that includes at least a pair of intake passages that serve each chamber of the engine. The flow through one of these passages is throttled or substantially restricted at low and medium engine speeds so as to provide a relatively small effective cross-sectional area. The throttling is diminished at high engine speeds so as to achieve maximum power output. Although this arrangement has certain advantages, it has not provided an optimum torque curve throughout the entire engine load and speed ranges as is desired.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is another object of this invention to provide an engine induction system that will improve the torque curve throughout the entire engine running conditions and particularly at mid ranges.
In connection with high performance engines, it is the practice to provide a substantial overlap between the opening of the intake valve and the closing of the exhaust valve. This insures good breathing and good scavenging at high speed but presents considerable problems in connection with low speed running. Because of the wide overlap, the exhaust gases tend to flow back into the intake passage and thus weaken the next inducted fuel/air charge.
It is, therefore, a still further object of this invention to provide an improved induction system that will preclude against this condition while at the same time permit the use of overlapping valve timing.